Micro fluidic device and method for producing micro fluidic device

ABSTRACT

A micro fluidic device comprises a micro channel in which a plurality of fluids form laminar flows and are supplied, wherein an inner wall of the micro channel comprise a protruding part that is substantially parallel to the flows of the fluids and protrudes in directions substantially vertical to interfaces formed by the plurality of fluids.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2007-080768 filed Mar. 27, 2007.

BACKGROUND

(i) Technical Field

The present invention relates to a micro fluidic device, and moreparticularly to a micro fluidic device having a micro channel and amethod for producing the micro fluidic device.

(ii) Related Art

In micro channel, since fluids are apt to form laminar flows and easilyflow, the laminar flows can be formed in which two liquids flow under astate that they are not mixed and kept separated from each other. Toincrease a contact time between the fluids, the channel needs to belengthened. In a restricted space, curved places are provided to foldthe channel and lengthen the channel. However, in the curved place, aconvection called a Dean vortex is generated due to a centrifugal force(see Shinichi Ohkawara and other three members, chemical EngineeringTheses, Vol. 30, No. 2, p. 135 to 140 (2004)).

Especially, in the laminar flows having micro particles dispersed, themicro particles move to the outside wall at the curved place so that anunexpected mixture or a mal-distribution of the particles is liable toarise.

SUMMARY

According to an aspect of the invention, there is provided a microfluidic device comprising a micro channel in which a plurality of fluidsform laminar flows and are supplied, wherein an inner wall of the microchannel comprise a protruding part that is substantially parallel to theflow direction of the fluids and protrudes in directions substantiallyvertical to interfaces formed by the plurality of fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figure, wherein:

FIG. 1 is a schematic plan view showing an exemplary embodiment of amicro fluidic device of the present invention;

FIG. 2 is an enlarged view including a curved place of the micro fluidicdevice shown in FIG. 1;

FIGS. 3A to 3C are sectional views taken along a line X-X′ of the microfluidic device shown in FIG. 2;

FIGS. 4A to 4E are sectional views of the micro fluidic device shown inFIG. 2;

FIGS. 5A and 5B are sectional views showing another example of a curvedplace in the micro fluidic device of the present invention;

FIGS. 6A to 6C are explanatory views of thin film patterns for forming apart shown in FIG. 2; and

FIGS. 7A to 7F are fabrication process diagrams showing one exemplaryembodiment of a method for fabricating a micro fluidic device preferablyusable for the present invention.

DETAILED DESCRIPTION

A micro fluidic device of the present invention has a micro channel inwhich a plurality of fluids form laminar flows and are supplied and ischaracterized in that protruding parts are formed on the inner walls ofthe micro channel that are substantially parallel to the flow directionof the fluids and protrude in directions substantially vertical tointerfaces formed by the plurality of fluids.

Since the micro fluidic device includes the protruding parts formed onthe inner walls of the micro channel that are substantially parallel tothe flow direction of the fluids and protrude in the directionssubstantially vertical to the interfaces formed by the plurality offluids, the laminar flows of the flows are held, and an unexpectedmixture or a mal-distribution of particles in the fluids hardly arises.Therefore, the stable laminar flows can be obtained.

The micro fluidic device of the present invention is not especiallylimited to a use and may be usable for various kinds of well-known uses.A channel length, a flow velocity, a kind of fluid, temperature or thelike are preferably suitably selected depending on the use.Specifically, the micro fluidic device may be used as an analyzingdevice in a medical field, producing, classifying and cleaning devicesof micro particles and a chemical reaction device, for instance, asynthesizing device or a polymerizing device.

In the present invention, the micro channel means a very small channelfor supplying an extremely small quantity of liquid or gas and the widththereof is located within a range of several μm or more to severalthousand μm or smaller. In the present invention, the micro channelmeans a channel of a micro-meter scale and further includes a channel ofa milli-meter scale.

The width of the channel may be suitably selected depending on apurpose. A range of 10 μm or more to 1000 μm or smaller is preferableand a range of 20 μm or more to 500 μm or smaller is more preferable.

In the present invention, since the micro channel is of the micro scale,both a dimension and a flow velocity are small. The Reynolds number (Re)of the fluids flowing in the micro channel is 2,300 or smaller.Accordingly, the micro fluidic device having the micro channel of themicro scale is not governed by turbulent flows, but by the laminarflows.

Here, the Reynolds number is represented by a below-described equation.When the Reynolds number is 2,300 or smaller, the micro fluidic deviceis governed by the laminar flows.

Re=uL/ν (u: flow velocity, L: length, ν:coefficient of kinematicviscosity)

To maintain governance by the laminar flows, the micro fluidic device ofthe present invention has the protruding parts formed on the inner wallsof the micro channel that are substantially parallel to the flowdirection of the fluids and protrude in the directions substantiallyvertical to the interfaces formed by the plurality of fluids.

In the micro fluidic device of the present invention, the plurality offluids form the laminar flows and are supplied. In the micro fluidicdevice, two or more fluids are preferably supplied from a plurality offluid inlet ports and a merged part forming the laminar flows ispreferably provided. Further, the micro fluidic device of the presentinvention includes one or more outlet ports and preferably has aplurality of outlet ports corresponding to the laminar flows.

In the present invention, the micro channel is a channel that has a verysmall diameter and is isolated from an outer part by a base material.The base material may be a base board or a tubular material.

In the present invention, the form of the micro channel is notespecially limited, however, ordinarily is tubular. Further, a sectionalform of the micro channel is not especially limited and any of forms maybe employed. As a sectional shape of a plane intersecting at rightangles to the axis of a channel of the micro channel, exemplified are acircular form, an elliptical form, a semi-circular form, a rectangularform, a triangular form, other polygonal forms, a tumbler form. However,the present invention is not limited thereto. The sectional shape of themicro channel is preferably rectangular among them, because the microfluidic device can be easily manufactured.

Further, in the present invention, a part or all of the micro channelincludes the protruding parts formed on the inner walls that aresubstantially parallel to the flow direction of the fluids and protrudein the directions substantially vertical to the interfaces formed by thefluids. That is, in the present invention, the micro channel ispreferably a micro channel that has the protruding parts in a part ofthe inner walls and the rectangular sectional shape.

Further, in the present invention, the shape of the axis of the channelis not especially limited and any of forms such as a straight line or acurve may be employed. Here, the form of the axis of the channel meansan axis of a flowing direction of the fluid in the micro channel.

As described above, the shape of the axis of the channel is notespecially limited. However, to ensure a channel length for a prescribedarea, a curved place is preferably formed. The curved place means a partthat changes the direction of a flow by providing a folded shape, acircular arc shape or an angled shape in the axis of the channel of themicro channel. Particularly, in the present invention, the curved placepreferably has the circular arc shape. As one example of the circulararc shape, the semi-circular form may be exemplified.

Namely, the form of the axis of the channel entirely includes thestraight line part and the curved place and is preferably designed sothat the channel length of the micro channel is large in the prescribedarea.

The forms of the protruding parts provided on the inner walls of themicro channel are not especially limited, however, they are provided tobe substantially parallel to the flow direction of the fluids. In thepresent invention, the protruding parts are provided to be substantiallyparallel to the flow direction of the fluids, however, the protrudingparts do not need to be exactly parallel to the flow direction of thefluids and an angle can be selected within such a range as not toprevent the flows of the fluids. In the present invention,“substantially parallel to the flow direction of the fluids” means anangle of 10 degrees or smaller with respect to the flow direction of thefluids. The angle is preferably 5 degrees or smaller, more preferably 3degrees or smaller and furthermore preferably 0 degree with respect tothe flow direction of the fluids, namely, parallel to the flow directionof the fluids.

For instance, when the sectional forms of the micro channel vertical tothe flow direction of the fluids are rectangular, one protruding partpreferably protrudes from one side at right angles to an inner part ofthe channel. Further, when an opposed protruding part is provided, theother protruding part preferably similarly protrudes at right angles toan opposite side from a corresponding position on the opposite side.Further, as described below, the protruding parts protrude substantiallyvertically to the interfaces formed by the fluids.

In the present invention, the protruding parts provided in the innerwalls of the micro channel protrude substantially in vertical directionsto the interfaces formed by the plurality of fluids. In the presentinvention, the protruding parts are provided substantially vertically tothe interfaces formed by the fluids, however, the protruding parts donot need to be exactly vertical to the interfaces, and an angle can beselected within such a range as not to prevent the deformation of theinterfaces of fluids. In the present invention, “protrude in thedirections substantially vertical to the interfaces formed by theplurality of fluids” means that a deviation from an angle of 90 degreesis an angle of 10 degrees or smaller. The deviation from the angle of 90degrees is preferably 5 degrees or smaller, more preferably 3 degrees orsmaller and furthermore preferably 0 degree with respect to theinterfaces formed by the fluids, that is, right angled to theinterfaces.

When three or more laminar flows are formed and two or more interfacesare present, the protruding parts may protrude in the directionssubstantially vertical to at least one interface, however, morepreferably protrude in the directions substantially vertical to all theinterfaces and the interfaces are preferably formed so as to satisfy theabove-described conditions.

As the shapes of the protruding parts, flat plate shapes may beemployed, or the height of the protruding parts may be decreased orincreased more toward the end of the channel from the inner walls.Further, the height of the protruding parts may be gradually increasedor decreased more toward the direction of the axis of the channel. Asthe shapes of the protruding parts, the protruding parts preferably havethe same height from the inner walls to the end of the channel and havethe rectangular shapes on the perpendicular plane to the axis of thechannel, and rectangular plate forming protruding parts are morepreferably provided among them.

Here, the “protruding parts” mean plate-shaped structures that stick outfrom the inner walls of the channel and extend in the directions of theaxis of the channel.

Further, the protruding parts may be provided continuously in thedirections of the axis of the channel from the inlet ports to the outletports of the channel and may be interrupted halfway.

Further, the protruding parts may be provided at any part of the sectionof the channel and provided on an upper surface and a lower surfacedepending on the directions of the interfaces formed by the laminarflows. However, the protruding parts are preferably provided in thedirection of the axis of the channel at parts corresponding to the innerwalls of an outer peripheral side of the curved places of the channeland the inner walls of an inner peripheral side thereof. Namely, theprotruding parts are preferably provided in the inner walls of thechannel in the outer peripheral side and the inner peripheral side ofthe curved places in terms of a centrifugal force. At this time, thelaminar flows are formed in the side-by-side manner, which means outerperipheral side and the inner peripheral side.

In the present invention, the protruding parts are preferably providedonly in the curved places and more preferably provided only in the innerwalls of the outer peripheral side of the curved places of the channel.When the protruding parts are arranged as described above, convection inthe curved places can be preferably prevented to more stabilize thelaminar flows and restrain the fluids to being mixed.

Only one protruding part may be provided and a plurality of protrudingparts may be provided in the inner wall of the channel. Namely, aplurality of parallel protruding parts may be provided on the samesection in the channel. In such a case, one or more to five or smallerprotruding parts are preferably provided and one or more to three orsmaller protruding parts are more preferably provided.

That is, in the present invention, the plurality of protruding parts ispreferably provided in the inner walls of the outer peripheral side ofthe curved places of the channel. Especially, in the case of the microfluidic device having a plurality of curved places, the plurality ofprotruding parts are preferably provided in the inner walls of the outerperipheral side of all the curved places.

The height of the protruding part is preferably 50% or smaller as wideas the width of the channel. Here, the “height of the protruding part”means the height of the protruding part when it is assumed that a widthfrom the inner wall of the channel to the inner wall of the channelopposed thereto in the direction vertical to the axis of the channel isset to 100%. The height of the protruding part is more preferably set to5% or more to 50% or less and furthermore preferably set to 10% or moreto 25% or less.

The height of the protruding part is preferably set to 50% or less aswide as the width of the channel so that stable laminar flows can beobtained.

Now, the present invention will be described in detail by referring toFIGS. 1 to 7F.

The same reference numerals used below designate the same components.

FIG. 1 is a schematic plan view showing a preferred example of the microfluidic device of the present invention.

In a substrate 22, a micro channel 20 is provided. In the micro channel20 of the micro fluidic device 10, inlet ports 24A and 24B forintroducing a fluid A and a fluid B respectively, and outlet ports 26Aand 26B for discharging the fluid A and the fluid B respectively, areprovided.

In FIG. 1, an exemplary embodiment for introducing the two fluids isshown, however, the present invention is not limited thereto and threeor more fluids may be introduced. Further, one kind of the fluids may bea micro particle dispersion liquid and the micro fluidic device may beused as a classifying device of micro particles or a cleaning device ofmicro particles. As the fluid, both gas and liquid can be used. In thepresent invention, as the fluid, the liquid is preferable.

In FIG. 1, the two liquids (the fluid A and the fluid B) are introducedfrom the inlet ports 24A and 24B and supplied to one micro channel 20 aslaminar flows. In FIG. 1, the two liquids (in FIG. 1, the fluid A andthe fluid B) supplied to the micro channel 20 subsequently flows in onemerged channel as the laminar flows.

Then, the fluid A and the fluid B are respectively discharged from theoutlet ports 26A and 26B. In the present invention, the number of theoutlet ports is not especially limited and one or more outlet ports maybe provided and the number of the outlet ports may be suitably selecteddepending on its purpose. Further, a plurality of outlet ports may beprovided along the channel or the outlet ports may be separatelyprovided on upper and lower parts of the channel.

In FIG. 1, to form the micro channel having a sufficient length on thesubstrate of the same area, a curved place 30 is provided. Otherpositions except the curved place form a straight line part 32. However,the micro fluidic device of the present invention is not limitedthereto, and, for instance, a curved place such as a zigzag part may beprovided.

FIG. 2 is an enlarged view including the curved place of the microfluidic device shown in FIG. 1.

In FIG. 2, the fluid A is supplied in an outer peripheral side of thecurved place 30 of the channel and the fluid B is supplied in an innerperipheral side of the curved place 30 of the channel. An interface 55is formed between the two fluids.

FIG. 3A shows a cross-sectional view taken along a line X-X′ of themicro channel shown in FIG. 2. In FIG. 3A, the micro channel 20 includesan inner wall 40 in the inner peripheral side of the curved place, aninner wall 42 in the outer peripheral side of the curved place, an upperwall 44 and a lower wall 46 and has a channel width W.

In a usual micro channel (see FIG. 3C), since a protruding part is notprovided, an unexpected mixture (shown by arrow marks) of a fluid A anda fluid B arises due to a centrifugal force in a curved place so thatthe fluid A and the fluid B passing the curved place are mixed togetherin an interface between them.

FIG. 3A shows one example of a cross-sectional view of the micro channel20 at the curved place 30 of the micro fluidic device 10 of the presentinvention. Here, the fluid A and the fluid B are supplied and curvedfrom a front side of this sheet to an interior to form the interface 55.In the inner wall 40 in the inner peripheral side at the curved place ofthe micro channel 20 and the inner wall 42 in the outer peripheral sideat the curved place, rectangular plate shaped protruding parts 50 areprovided that are parallel to the flow direction of the fluids andvertical to the interface 55.

In FIG. 3A, three pairs of the protruding parts 50 are provided inparallel with the flow direction of the fluids, however, the presentinvention is not limited thereto. One or more protruding parts 50 may beprovided and the number of the protruding parts to be provided may bepreferably selected so as to obtain stable laminar flows. Further, asdescribed above, the sectional form of the protruding part may bedesigned so that the height thereof is increased from the curved placeto the inner part of the channel or conversely decreased from the curvedplace to the inner part of the channel.

Further, the height W′ of the protruding part provided in the inner wallin the outer peripheral side at the curved place and the height W″ ofthe protruding part provided in the inner wall in the inner peripheralside at the curved place are preferably respectively 50% or smaller ashigh as the channel width W, more preferably 5% or more to 50% or lessand furthermore preferably 10% or more to 25% or less. The height of theprotruding parts is preferably located within the above-described range,so that the stable laminar flows can be maintained.

Further, as W′ and W″, the same height may be used or different heightmay be selected.

Further, as shown in FIG. 3A, when the protruding parts are provided inboth the opposed inner walls, the total of the height of the protrudingparts (W′+W″) is preferably 60% or smaller as high as W, more preferably10% or more to 50% or less, and furthermore preferably 20% or more to40% or less. The total of the height of the protruding parts ispreferably located within the above-described range, so that the stablelaminar flows can be formed without decreasing the velocity of thelaminar flows.

As shown in FIG. 3A, when the protruding parts are provided in both theopposed inner walls, the opposed protruding parts may be provided at anypositions, and may be preferably provided in parallel. That is, theprotruding parts are preferably provided so as to have the same heightwith respect to the direction of height (in FIGS. 3A to 3C, a directionfor connecting the upper surface to the lower surface) from thesubstrate of the micro channel. The protruding parts are preferablyarranged as described above, so that the stable laminar flows can beformed.

The thickness a of the protruding part and a space b between theprotruding parts can be suitably selected depending on a purpose andpreferably suitably selected so as to obtain the stable laminar flows.W′/b is preferably 3 or smaller and more preferably 1.5 or smaller.

Further, as shown in FIG. 3A, when the plurality of protruding parts 50are provided, the shapes of the protruding parts, the height W′ and W″of the protruding parts and the thickness a of the protruding parts maybe respectively the same or different and preferably suitably selected.Further, when three or more protruding parts are provided, the space bbetween the two or more protruding parts may be respectively the same ordifferent and preferably suitably selected.

FIG. 3B shows another preferred example of a section taken along a lineX-X′ of FIG. 2.

In FIG. 3B, the protruding parts 50 are provided only in the inner wallin the outer peripheral side of the curved place. In this case, theheight W′ of the protruding part 50 is preferably set to 50% or smalleras high as the width W of the micro channel 20. The height W′ of theprotruding part 50 is preferably located within the above-describedrange so that a convection due to the centrifugal force can be preventedand the stable laminar flows can be formed.

The above-described preferred height of W′ and W″ means a maximum heightand the maximum height of the protruding parts provided in the microchannel is preferably located within the above-described range. Asdescribed below, the protruding part having the maximum height in acentral part of the curved place is preferable.

The protruding parts 50 are not limited to the above-describedprotruding parts and may be provided in the upper surface 44 or thelower surface 46 of the micro channel 20 as described below. However,for the purpose of obtaining the stable laminar flows, the protrudingparts 50 are preferably provided in the inner wall 40 in the innerperipheral side of the curved place and/or the inner wall 42 in theouter peripheral side of the curved place as shown in FIG. 3A or FIG.3B. Especially, as shown in FIG. 3B, the protruding parts are preferablyprovided in the inner wall 42 in the outer peripheral side of the curvedplace as shown in FIG. 3B.

In the present invention, the protruding part provided in the curvedplace is preferably provided in such a way that the height of theprotruding part reaches a maximum at the center of the curved place, andthe height of the protruding part becomes gradually lower toward theboth ends of the curved place.

Now, a description will be given by referring to FIG. 4A to 4E. FIGS. 4Ato 4E show sectional views of the micro channel shown in FIG. 2. FIG. 4Ashows a section taken along a line M-M′ before the curved place 30. Inthis section, the protruding part is not provided. The protruding partis provided so that its height is gradually increased from the partbefore the curved place. In a section taken along a line N-N′ shown inFIG. 4B, the protruding parts having low height are provided. In asection (FIG. 4C) taken along a line X-X′ at the center of the curvedplace, the height of the protruding parts is the highest. Further, theheight of the protruding parts is provided so as to be gradually lowtoward the end of the curved place. In a section taken along a line P-P′shown in FIG. 4D, the protruding parts are provided that have the heightlower than that of the section taken along the line X-X′. Further, asshown in FIG. 4E, in a section taken along a line Q-Q′ as the finish ofthe curved place, the protruding part is not provided. Namely, assumingthat in the N-N′ section, the X-X′ section and the P-P′ section, theheight of the protruding parts provided in the inner wall in the outerperipheral side is respectively Wb′, Wc′, and Wd′ and the height of theprotruding parts provided in the inner wall in the inner peripheral sideis respectively Wb″, Wc″, Wd″, relations of Wb′<Wc′>Wd′ and Wb″<Wc″>Wd″are established.

Now, referring to FIGS. 5A and 5B, one exemplary embodiment of the microfluidic device of the present invention will be described in which twofluids are supplied in upper and lower parts on a section vertical to adirection of an axis of a channel.

FIG. 5A is another example showing a section of a channel in a curvedplace of the micro fluidic device of the present invention.

In FIG. 5A, two fluids designated by a fluid A and a fluid B formlaminar flows and are curved and supplied from a front side of a sheetsurface to an interior. FIG. 5A shows the section of the channel in thecurved place and the channel 20 includes an inner wall 40 in the innerperipheral side of the curved place, an inner wall 42 in the outerperipheral side of the curved place, an upper surface 44 and a lowersurface 46.

In the inner wall of the channel, protruding parts 50 are provided thatprotrude in the directions vertical to an interface 55 formed by thefluid A and the fluid B. The protruding parts 50 are formed in parallelwith the flow direction of the fluids and curved from the front side ofthe sheet surface to the interior in FIG. 5A.

The height W2′ and W2″ of the protruding parts to be formed isrespectively 50% or smaller as high as a channel width W2, morepreferably 5% or more to 50% or less and furthermore preferably 10% ormore to 25% or less. The height of the protruding parts is preferablylocated within the above-described range, so that the stable laminarflows can be maintained. Further, as W2′ and W2″, the same height may beused or different height may be selected.

Further, as shown in FIG. 5A, when the protruding parts are provided inboth the opposed inner walls, the total of the height of the protrudingparts (W2′+W2″) is preferably 60% or smaller as high as the width W2 ofthe channel, more preferably 10% or more to 50% or less, and furthermorepreferably 20% or more to 40% or less. The total of the height of theprotruding parts is preferably located within the above-described range,so that the stable laminar flows can be formed without decreasing thespeed of the laminar flows.

Further, the width a of the protruding part and a space b between theprotruding parts can be suitably selected as described above.

Further, when the two upper and lower laminar flows are formed, theheight of the protruding parts is preferably provided so as to bemaximum in the center of the curved place. The state thereof isdescribed above.

FIG. 5B shows a secondary flow velocity vector generated in the sectionof the channel shown in FIG. 5A. As shown in FIG. 5A, when the fluidsare arranged in the upper and lower parts, a pair of Dean eddies areformed in the upper and lower parts. An area where a secondary flowvelocity is the highest is located in the intermediate parts of theupper and lower Dean eddies. In the curved place, since such a secondaryflow velocity distribution is generated, especially when particles areincluded in the fluids, the uneven distribution (mal-distribution) ofthe particles may possibly arise.

In the present invention, the protruding parts are provided as describedabove, so that the uneven distribution of the particles can besuppressed and the laminar flows can be formed in a stable way.

In the present invention, the micro fluidic device may be manufacturedby any of methods. Now, a method for fabricating the micro fluidicdevice preferable and usable for the present invention will be describedbelow.

The micro fluidic device of the present invention is preferably formedby laminating thin film pattern members on which prescribedtwo-dimensional patterns are formed. The thin film pattern members aremore preferably laminated under a state that the surfaces of thin filmscome into direct contact with each other and are bonded together.

As a preferred method for producing the micro fluidic device of thepresent invention, can be exemplified a method for producing a microfluidic device comprising:

(i) a step (a donor substrate forming step) of forming a plurality ofthin film pattern members respectively corresponding to sectional formsof a predesignated micro fluidic device on the donor substrate; and(ii) a step (a bonding step) of repeatedly bonding the donor substrateon which the plurality of thin film pattern members are formed to andseparating the donor substrate from a second substrate to transfer theplurality of thin film pattern members on the second substrate.

The method for producing the micro fluidic device of the presentinvention will be described in more detail.

(Donor Substrate Forming Step)

In the present invention, a donor substrate is preferably formed by anelectro-forming method. Here, the donor substrate indicates a substrateon which the plurality of thin film patterns respectively correspondingto the sectional forms of the target micro fluidic device are formed onthe first substrate. The first substrate is preferably made of metal,ceramics or silicon and metal such as stainless steel may be preferablyused.

Initially, the first substrate is coated by a thick film photo-resist.The photo-resist is exposed by a photo-mask which includes the sectionalforms of the micro fluidic device to be produced. Then the photo-resistis developed. Then, the substrate having the resist patterns is immersedin a plating bath to allow, for instance, a nickel plating to grow onthe surface of the metal substrate that is not covered with thephoto-resist. The thin film patterns may be formed with copper or nickelby using the electro-forming method.

Then, the resist patterns are removed to form the thin film patternsrespectively corresponding to the sectional forms of the micro fluidicdevice on the first substrate.

FIGS. 6A to 6C are explanatory views of the thin film patterns forforming the part shown in FIG. 2. FIG. 6A shows a sectional form takenalong a line X-X′ of the curved place shown in FIG. 2. FIG. 6A and FIG.6B show that the micro fluidic device having three protruding parts isformed by laminating in order a total of 11 thin film patterns including501A₁, 502B₁, 502B₂, 503C₁, 502B₃, 503C₂, 502B₄, 503C₃, 502B₅, 502B₆ and501A₂.

FIG. 6C shows only a part of a curved place of the donor substrate. Thethin film patterns 501A₁ and 501A₂ provided on the first substrate 500respectively correspond to parts that form the upper surface and thelower surface of a micro channel. The thin film patterns 503C₁, 503C₂and 503C₃ correspond to parts at which the protruding parts are located.The thin film patterns 502B₁, 502B₂, 502B₃, 502B₄,,,,, correspond toparts of the micro channel in which the protruding parts are notprovided.

(Bonding Step)

The bonding step means a step for repeatedly bonding the first substrate(the donor substrate) and the second substrate (the target substrate)and separating the both substrate each other to transfer the pluralityof thin film patterns on the donor substrate onto the target substrate.A bonding operation is preferably carried out by a room-temperaturebonding method or a surface activated bonding method.

FIGS. 7A to 7F show fabrication process diagrams showing one exemplaryembodiment of the method for fabricating the micro fluidic device thatcan be preferably usable for the present invention.

First, as shown in FIG. 7A, the donor substrate 505 is attached on alower stage in a vacuum chamber that is not shown in the drawing. Thetarget substrate 510 is attached on an upper stage in the vacuum chamberthat is not shown in the drawing. Subsequently, the air in the vacuumchamber is exhausted to obtain a high vacuum state or an ultra-highvacuum state. Then, the lower stage is moved relatively to the upperstage to locate the thin film pattern 501A₁ of a first layer of thedonor substrate 505 just below the target substrate 510. Then, an argonatom beam is irradiated on the surface of the target substrate 510 andthe surface of the thin film pattern 501A₁ of the first layer to cleanthe surfaces.

Then, as shown in FIG. 7B, the upper stage is lowered to press thetarget substrate 510 and the donor substrate 505 for a prescribed time(for instance, 5 minutes) with a prescribed load force (for instance, 10kgf/cm²) and the target substrate 510 is bonded (a surface activatedbonding) onto the thin film pattern 501A₁ of the first layer under aroom temperature. In this exemplary embodiment, the thin film patternsare laminated in order of 501A₁, 502B₁, 502B₂, 503C₁, 502B₃, 503C₂,502B₄, 503C₃, 502B₅, 502B₆ and 501A₂.

Then, as shown in FIG. 7C, when the upper stage is lifted to separatethe donor substrate from the target substrate, the thin film pattern501A₁ of the first layer is peeled off from the first substrate (thedonor substrate) 500 and transferred to the target substrate 510 side.This phenomenon arises, because an adhesive strength between the thinfilm pattern 501A₁ and the target substrate 510 is larger than anadhesive strength between the thin film pattern 501A₁ and the firstsubstrate (the donor substrate) 500.

After that, as shown in FIG. 7D, the lower stage is moved to locate thethin film pattern 502B₁ of a second layer on the donor substrate 505just below the target substrate 510. Then, the surface of the thin filmpattern 501A₁ (a surface which was in contact with the first substrate500) transferred to the target substrate 510 side and the surface of thethin film pattern 502B₃ of the second layer are cleaned as describedabove.

Then, as shown in FIG. 7E, the upper stage is lowered to bond the thinfilm pattern 501A₁ of the first layer to the thin film pattern 502B₁ ofthe second layer. As shown in FIG. 7F, when the upper stage is lifted,the thin film pattern 502B₁ of the second layer is peeled off from themetal substrate (the first substrate) 500 and transferred to the targetsubstrate 510 side.

The donor substrate 505 and the target substrate 510 are repeatedlypositioned, bonded to and separated from each other so that theplurality of thin film patterns such as other thin film patterns (502B₂,503C₁, 502B₃, 503C₂, 502B₄, 503C₃, 502B₅, 502B₆ and 501A₂) respectivelycorresponding to the sectional forms of the micro fluidic device aretransferred to the target substrate. When a laminated body transferredto the target substrate 510 is detached from the upper stage and thetarget substrate 510 is removed, the micro fluidic device shown in FIGS.6A to 6C is obtained.

The present invention is not limited to the above-described exemplaryembodiment and may be variously modified within a range withoutdeparting the gist of the present invention. The components of theexemplary embodiments may be arbitrarily combined within the rangewithout departing the gist of the present invention.

In the above-described exemplary embodiments, the donor substrate ismanufactured by using the electro-forming method, however, the donorsubstrate may be formed by using a semiconductor process. For instance,a substrate made of a Si wafer is prepared. On this substrate, a moldreleasing layer made of polyimide is formed by a spin coating method. Onthe surface of the mold releasing layer, an Al thin film as a componentmaterial of a micro fluidic device is formed by a sputtering method. Thealuminum thin film is patterned by a photo-lithography method so thatthe donor substrate can be formed.

1. A micro fluidic device comprising a micro channel in which aplurality of fluids form laminar flows and are supplied, wherein aninner wall of the micro channel comprise a protruding part that issubstantially parallel to the flow direction of the fluids and protrudesin directions substantially vertical to interfaces formed by theplurality of fluids.
 2. A micro fluidic device according to claim 1,wherein the micro channel comprises a curved place, and the protrudingpart is provided in the curved place of the micro channel.
 3. A microfluidic device according to claim 2, wherein the protruding part isprovided only in the inner wall of an outer peripheral side of thecurved place of the micro channel.
 4. A micro fluidic device accordingto claim 1, wherein a height of the protruding part is 50% or smallerthan a width of the micro channel.
 5. A micro fluidic device accordingto claim 1, wherein the micro fluidic device is formed by laminatingthin film pattern members.
 6. A method for producing a micro fluidicdevice according to claim 1, comprising: forming, on a first substrate,a plurality of thin film pattern members each of which is to constitutea sectional form of the micro fluidic device; and repeatedly bonding thefirst substrate, on which the plurality of thin film pattern members areformed, to and separating the first substrate from a second substrate,so as to transfer said plurality of thin film pattern members on thesecond substrate.
 7. A method for producing a micro fluidic deviceaccording to claim 6, wherein the first substrate is bonded to thesecond substrate by a room-temperature bonding method or a surfaceactivated bonding method.
 8. A method for producing a micro fluidicdevice according to claim 6, wherein said plurality of thin filmpatterns are formed on the first substrate by an electro-forming method.9. A method for producing a micro fluidic device according to claim 6,wherein the thin film pattern members comprise nickel, an alloyincluding nickel as a main component, copper or an alloy includingcopper as a main component.